This invention pertains to a non-ferrous metal mold plug activation system and bleedout detection and plug off system, which stops the flow of metal during predetermined conditions, such as during the initial introduction of molten metal to the molds or in the event a bleedout is detected in the mold.
Metal ingots and billets are typically formed by a casting process, which utilizes a vertically oriented mold situated above a large casting pit beneath the floor level of the metal casting facility. The lower component of the vertical casting mold is a starting block mounted on starting block pedestals. When the casting process begins, the starting blocks are in their upward-most position and in the molds. As molten non-ferrous metal is poured into the mold and cooled, the starting block is slowly lowered at a pre-determined rate by a hydraulic or pneumatic cylinder or other device. As the starting block is lowered, solidified non-ferrous metal or aluminum emerges from the bottom of the mold and ingots or billets are formed.
While the invention applies to casting of metals in general, including without limitations aluminum, brass, lead, zinc, magnesium, copper, steel, etc., the examples given and preferred embodiment disclosed are for aluminum, and therefore the term aluminum will be used throughout for consistency even though the invention applies more generally to metals.
While there are numerous ways to achieve and configure a vertical casting arrangement, FIG. 1 illustrates one example. In FIG. 1, the vertical casting of aluminum generally occurs beneath the elevation level of the factory floor in a casting pit. Directly beneath the casting pit floor 1a is a caisson 3, in which the pneumatic or hydraulic cylinder barrel 2 for the hydraulic cylinder is placed.
As shown in FIG. 1, the components of the lower portion of a typical vertical aluminum casting apparatus, shown within a casting pit 1 and a caisson 3, are a hydraulic cylinder barrel 2, a ram 6, a mounting base housing 5, a platen 7 and a starting block base 8, all shown at elevations below the casting facility floor 4.
The mounting base housing 5 is mounted to the floor 1a of the casting pit 1, below which is the caisson 3. The caisson 3 is defined by its side walls 3b and its floor 3a. 
A typical mold table assembly 10 is also shown in FIG. 1, which can be tilted as shown by hydraulic cylinder 11 pushing mold table tilt arm 10a such that it pivots about point 12 and thereby raises and rotates the main casting frame assembly, as shown in FIG. 1. There are also mold table carriages which allow the mold table assemblies to be moved to and from the casting position above the casting pit.
FIG. 1 further shows the platen 7 and starting block base 8 partially descended into the casting pit 1 with billet 13 being partially formed. Billet 13 is on starting block 14, which is mounted on pedestal 15. While the term starting block is used for item 14, it should be noted that the terms bottom block and starting head are also used in the industry to refer to item 14, bottom block typically used when an ingot is being cast and starting head when a billet is being cast.
While the starting block base 8 in FIG. 1 only shows one starting block 14 and pedestal 15, there are typically several of each mounted on each starting block base, which simultaneously cast billets, special shapes or ingots as the starting block is lowered during the casting process.
When hydraulic fluid is introduced into the hydraulic cylinder at sufficient pressure, the ram 6, and consequently the starting block base 8, are raised to the desired elevation start level for the casting process, which is when the starting blocks are within the mold table assembly 10.
The lowering of the starting block base 8 is accomplished by metering the hydraulic fluid from the cylinder at a pre-determined rate, thereby lowering the ram 6 and consequently the starting blocks at a pre-determined and controlled rate. The mold is controllably cooled during the process to assist in the solidification of the emerging ingots or billets, typically using water cooling means.
There are numerous mold and casting technologies that fit into these mold tables. Some are generally referred to as xe2x80x9chot topxe2x80x9d technology, while others are more conventional casting technologies that use floats and downspouts, both of which are known to those of ordinary skill in the art. The hot top technology generally includes a refractory system and molten metal trough system located on top of the mold table, whereas the conventional pour technology involves suspending or supporting the source of molten metal above the mold table and the utilization of down spouts or tubes and floats to maintain the level of molten metal in the molds while also providing molten metal to the molds.
These different casting technologies have different advantages and disadvantages and produce various billet qualities, but no one of which is required to practice this invention.
The metal distribution system is also an important part of the casting system. In the two technology examples given, the hot top distribution trough sits atop the mold table while the conventional pouring trough is suspended above the mold table to distribute the molten metal to the molds.
Mold tables come in all sizes and configurations because there are numerous and differently sized and configured casting pits over which mold table are placed. The needs and requirements for a mold table to fit a particular application therefore depends on numerous factors, some of which include the dimensions of the casting pit, the location(s) of the sources of water and the practices of the entity operating the pit.
The upper side of the typical mold table operatively connects to, or interacts with, the metal distribution system. The typical mold table also operatively connects to the molds which it houses.
When non-ferrous metal is cast using a continuous cast vertical mold, the molten metal is cooled in the mold and continuously emerges the lower end of the mold as the mold table is lowered. The emerging billet, ingot or other configuration is intended to be sufficiently solidified such that it maintains its desired shape. There is an air gap between the emerging solidified metal and the permeable ring wall. Below that, there is also a mold air cavity between the emerging solidified metal and the lower portion of the mold and related equipment.
Conditions may develop during the casting process which cause the molten aluminum to pass through the mold without sufficiently solidifying, such that instead of solidified metal emerging, molten metal leaks through. This is referred to as bleedout or breakout and not only creates a very dangerous condition, but causes substantial economic loss due to the physical damage that results and the downtime to the production line.
Systems directed to preventing or minimizing the effects of the bleedout situation must operate under very harsh conditions in the casting environment, conditions such as high heat, steam, exposure to molten metal, and exposure to corrosive elements in the air, to name a few.
Originally, workers were exposed to the dangerous bleedout condition because they were required to manually plug the mold entrance to prevent the further flow of molten metal through the mold experiencing the bleedout condition.
Other prior systems have been developed to attempt to remedy the well recognized problem. One example of such a prior system utilizes a relatively complicated optical sensor system which detects the presence of metal in the mold air cavity optically. Once a blockage is detected between a sensor positioned in the upper portion of the air gap and a sensor positioned in the lower portion of the air gap, a signal is sent to a controller. The optical sensors may also be positioned to detect molten metal in the mold air cavity. The controller generally receives the signal, interprets it and then sends a signal to a mold plug activation device, causing the mold plug to block the flow of metal to the mold. However, devices such as this are relatively complicated devices and involve placing sensors and controllers in the harsh casting environment, which is unnecessarily expensive, unduly complicated and not nearly as reliable as this invention.
Another example of such a prior system is one which places a heat sensing device or thermocouple in the mold air cavity, and then calibrating the thermocouple such that it sends a signal to a controller when a pre-determined temperature is reached. The temperature is pre-determined such that the signal is sent when a bleedout condition occurs. The sensor typically sends a signal to an electronic controller, which reads and interprets the signal, and then transmits another signal to a mold plug activation device, thereby causing the mold plug to block the flow of metal to the mold.
Examples of problems with these prior systems are: they require the use of an electronic or other controller to receive the signal from the sensor, interpret the signal, and then send a second signal to the mold plug activator; they do not operate reliably in such a harsh, hot and corrosive environment; they depend on reliably receiving a readable electrical signal of some sort from the sensor, in the harsh environment; they depend on the reliability of the controller, its ability to receive and interpret the signal, and its ability to then transmit a second to the mold plug activator; and there is an unacceptably long period of time during which the first signal is received and interpreted, and the second signal is transmitted to the mold plug activator.
Prior art systems simply depend on too many factors and components which do not operate reliably enough in a harsh environment, as well as too many components. The costs of the prior art systems are also higher than they need be, due to the number of components and the expense of attempting to provide if protection for the components from the operating environment.
It is also important in bleedout situations to stop the flow of metal very quickly, and in that regard, seconds and fractions of seconds can be critical. The prior system""s use of less than reliable sensors combined with intermediate controllers, results in too many components and too many steps to finally activate and move the metal flow stop device into the metal flow cavity. This relative slowness in prior systems allows an unnecessarily large quantity of molten metal to flow through the mold without solidifying. This molten metal can ruin other equipment and require a substantial cost in downtime, cleanup and repair, not to mention subjecting the operator(s) to more danger.
The forenamed recognized needs have not heretofore been sufficiently fulfilled by existing systems.
It is a primary object of this invention to provide a system which will operate reliably in a harsh environment. It is also an object of this invention to provide such a system which requires fewer components, and preferably fewer or no electronic components.
It is a further object of this invention to utilize components which are more reliable in the harsh operating environment of a metal casting facility, preferably to avoid using an electronic controller in particular.
It is a still further object of this invention to provide such a system which stops the flow of molten metal through the mold substantially faster than prior systems, when substantially faster can mean merely a fraction of a second.
If This invention accomplishes these objectives by providing a mold plug activation system wherein the sensor is preferably directly connected pneumatically, electrically, mechanically, or otherwise, to the mold plug activator. This invention preferably avoids the use of intermediate controllers between the sensor and the mold plug activator.
There is also a problem with existing mold tables during startup or during the initial introduction of molten metal to each of the molds. While it would be preferred to provide the metal to each of the mold cavities at approximately the same time, it is rarely achieved to the degree desired due to the flow times for the molten metal to flow through the troughs and get to each mold inlet. This can lead to casting problems when the platen is being lowered and some of the molds have not yet received the molten metal. Related to the need or ability to simultaneously stop the flow of metal to all molds on a table during a pre-determined event, is the ability of a system to block the flow of metal in the event of a power outage.
It is therefore also an objective of this invention to provide such a system which may also be used to provide molten metal to the numerous mold cavities at the same approximate time during startup. This is accomplished in one or more of the embodiments of the invention, wherein for instance in the hydraulic or pneumatic embodiment, the balancing hydraulic/pneumatic pressure can be introduced to each mold plug at the same time, thereby raising each of the mold plugs at the same time, after the molten metal has substantially filled all the applicable troughs. This invention further allows utilizes an activation system which may be placed in the normally closed position such that when power to the molds is lost, the metal flow stop devices move to block the continued flow of metal to the mold inlets.
This invention can also accomplish these objectives by providing a mold plug activation system wherein the sensor is sacrificed in the event of a mold bleedout, i.e. a disposable or sacrificial sensor, which is partially or wholly destroyed or sacrificed in the event of a bleedout.
In accomplishing these objectives, this invention provides a system which is simpler, more reliable and safer than all prior systems, and which should reduce the risk of injury to workers in casting facilities.